32 bit to 64 bit Safe!
I was working on a porting task from 32 bit to 64 bit. Man, its a hell of a job to do. Loads of data types and API's change over the two variants. There is a nice article by Microsoft which can be found here. I am not an expert in doing the porting though, but have learnt one fact: Write code that is 64 bit compatible even though you are targeting 32 bit. In doing so, the code will almost be compatible with 32 bit. As the industry has been moving towards making every piece of software 64 bit, by this approach we make sure that we have a working 32 bit as well a 64 bit code base.